Navigational Lights (PDF)

### **Luminous Range Explained Simply:** The **luminous range** is the **maximum distance** you can see a light based on: 1. The **nominal range** is the **maximum distance** a light can be seen in **clear weather** (visibility of 10 nautical miles). It applies to most lighted navigation...

### **Luminous Range Explained Simply:** The **luminous range** is the **maximum distance** you can see a light based on: 1. The **nominal range** is the **maximum distance** a light can be seen in **clear weather** (visibility of 10 nautical miles). It applies to most lighted navigation aids, except for: a. **Range lights** b. **Directional lights** c. **Private aids to navigation** 2. The **current weather visibility** (e.g., clear, foggy, or hazy conditions). #### **Key Points:** - If the weather is clear, you can see the light **further** than its nominal range. - If the weather is poor, you'll see it **closer** than its nominal range. Think of it as the **realistic range** for the light, adjusted for the current weather. LUMINOUS RANGE DIAGRAM Let me break this down for you step by step in simpler terms: 1. **Nominal Range**: a. This is the **maximum distance** a light can be seen when the weather visibility is **perfect (10 nautical miles)**. b. Think of it as a light\'s \"ideal\" range in clear weather. 2. **Real-world Visibility**: c. If the weather visibility is **less than 10 nautical miles** (like foggy conditions), you won\'t see the light as far as the nominal range. d. If the visibility is **better than 10 nautical miles** (like on a crystal-clear night), you may see the light **further** than the nominal range. 3. **Luminous Range**: e. This is the **actual distance** you can expect to see the light **based on the current weather visibility**. f. It adjusts the nominal range for real-world visibility conditions. 4. **The Diagram (or Chart)**: g. The chart helps you figure out the luminous range (actual range). h. Here's how you use it: a\. Start with the **nominal range** of the light (found in the light list). b\. Find the line that matches the current weather visibility (or somewhere between two lines if your visibility isn\'t exact). c\. Where the two meet, move left to the border of the chart to find the **luminous range**. ### ### **Example:** - A lighthouse has a nominal range of **15 nautical miles**. - If visibility is **8 nautical miles** (not perfect), the luminous range might only be **12 nautical miles**. - If visibility is **20 nautical miles** (very clear), the luminous range might increase to **18 nautical miles**. **Geographic Range of Visibility Explained Simply:** Geographic Range: The greatest distance the curvature of the earth permits an object of a given height to be seen from a particular height of eye without regard to luminous intensity or visibility conditions. The **geographic range** is how far you can see an object at sea, considering: 1. **The height of the object** above sea level (e.g., a lighthouse). 2. **The height of your eyes** above sea level (e.g., standing on a ship). #### **How It Works:** 1. Use the table to find the distance for the **object\'s height**. 2. Add the distance for your **eye height** from the table. 3. The total is the **geographic range** (how far away you can see the object). #### **Example:** - Lighthouse is 100 feet → 12 nautical miles. - Your eye height is 30 feet → 6 nautical miles. - Total: **18 nautical miles**. ### **Types of Navigation Signals (Simplified)** 1. **Lighted Aids to Navigation**: a. Operate automatically at night and turn off during the day. b. Not all lights turn on/off at the same time; double-check during twilight. c. Lights are serviced regularly but may sometimes malfunction. 2. **Lateral Significance (Red & Green Lights)**: d. **Green Lights**: i. Mark the **port side** of channels or obstructions to keep to your **port side**. ii. Used on preferred channel markers (preferred channel to **starboard**). e. **Red Lights**: iii. Mark the **starboard side** of channels or obstructions to keep to your **starboard side**. iv. Used on preferred channel markers (preferred channel to **port**). 3. **Non-Lateral Lights (White & Yellow)**: f. No lateral significance. g. Purpose is determined by their shapes, colors, letters, or light rhythms. 4. **Light Sectors**: h. Red sectors warn of dangers (shoals, obstructions, nearby land). i. Sectors provide approximate bearings but may not be precise. j. Always use a compass bearing for accuracy, as sector boundaries may appear blurred. 5. **Lighted Markers & Rhythms**: k. **Preferred Channel Marks**: 2 flashes + 1 flash (composite group flashing). l. **Safe Water Marks**: White Morse code "A" (short flash + long flash). m. **Isolated Danger Marks**: White flashing (2). n. **Special Marks**: Yellow light (flashing or fixed). o. **Regulatory Marks**: White light (any rhythm except quick flashing, flashing (2), or Morse code \"A\"). 6. **Quick Flashing Lights**: p. Used in cautionary areas like sharp turns, narrow channels, wrecks, or obstructions. 7. **Retroreflective Materials**: q. Increase visibility at night. Colors match the light color of the marker. ### **Simplified Definitions:** 1. **Luminous Range**: a. The **maximum distance** a light can be seen based on its brightness, weather visibility, and the observer's eyesight. 2. **Nominal Range**: b. The **luminous range** of a light in clear weather with 10 nautical miles visibility. 3. **Geographical Range**: c. The **maximum distance** a light can be seen, factoring in the Earth\'s curvature and the heights of the light and observer. 4. **Visibility of a Light**: d. How far a light can typically be seen in clear weather, measured in nautical miles. 5. **Range Lights**: e. Two or more lights at different heights that create a **line of sight** when aligned. f. The **front light** is closer and lower; the **rear light** is farther and higher. To calculate the **geographic visibility** (maximum distance at which an object can be seen): 1. Use the table to find the distance based on the **height of the object** above sea level. 2. Use the table again for the distance based on the **height of the observer\'s eye** above sea level. 3. **Add the two distances together** to get the total geographic visibility. For example, if the observer's eye is 55 feet above sea level, find the distance for 55 feet in the table, add it to the distance for the object's height, and you'll have the maximum visibility. ### **Simplified Definitions** #### **3.1 Light Signals** **General Terms**: - **Character**: The unique pattern of a light (e.g., fixed, flashing, alternating) that identifies it. - **Fixed Light**: Always on with no changes. - **Rhythmic Light**: A light with repeating cycles (flashes, alternating colors). - **Alternating Light**: Changes colors in each cycle. - **Period**: The time for one full light cycle. - **Phase**: A part of a light's cycle, like a flash or eclipse. - **Bearings**: Directions of light visibility given in clockwise order from the sea. **Descriptive Terms**: - **Aeronautical Light**: Bright, high lights for aircraft, often the first seen from sea. - **Aeromarine Light**: Marine light angled upward for aircraft navigation. - **Air Obstruction Light**: Red light marking hazards for aircraft. - **Daytime Light**: Operates 24/7, sometimes brighter during the day. - **Direction Light**: Marks a narrow path to follow, often with flanking sectors. - **Elevation**: Height of the light above sea level. - **Fog Detector Light**: Activates in fog; may flash, sweep, or show bluish light. - **Fog Light**: Operates only in fog. - **Structure Height**: Distance from ground to the top of the light structure. - **Leading Lights**: Two lights forming a navigational line. - **Lights in Line**: Lights marking boundaries but not for navigation alignment. - **Loom**: A glow from a light that's below the horizon. - **Luminous Intensity**: The brightness of a light in a specific direction. - **Main Light**: The primary light in a group. - **Occasional Light**: Used only in specific situations, like during fishing. - **Passing Light**: A small light on a structure to guide vessels when the main light isn't visible. - **Sector Light**: Shows different colors in various areas for navigation. - **Subsidiary Light**: A secondary light with a special function, like a passing light. - **Unwatched Light**: Operates automatically with occasional maintenance. #### **3.2 Sound Signals** **General Terms**: - **Sound Signal**: Audio signal for information or warnings. - **Fog Signal**: Sound for navigation in poor visibility. - **Morse Code Fog Signal**: Uses Morse Code characters. - **True Range**: The maximum distance a signal can be understood based on conditions. **Fog Signals and Systems**: - **Bell**: Rings a metal bell for sound. - **Diaphone**: Uses compressed air to make one or two tones, sometimes with a "grunt." - **Explosive Signals**: Sound produced by explosions. - **Gong**: A flat disc that makes a resonant sound. - **Horn**: Produces sound through tubes or vibrating parts: - **Klaxon**: A small hand-operated horn. - **Membrane Horn**: Vibrates a membrane using air, steam, or electricity. - **Nautophone**: Electrically activated horn. - **Reed Horn**: Uses a vibrating steel reed with compressed air. - **Typhon**: Uses steam or air to vibrate a membrane. - **Siren**: Produces a deep, wailing sound using rotating discs. - **Underwater Acoustic Signal**: Low-frequency sound for underwater navigation, detectable up to 50 nautical miles. - **Hooter**: Makes a sound with varying frequencies. - **Whistle**: Produces a high-pitched sound using air or steam. ### **4.6 Column 6 -- Range** **Light Ranges** - Ranges are given in nautical miles (M): - **Bold type**: Ranges 15 M or greater. - **Normal type**: Ranges less than 15 M. - If a light has different ranges for its sector colors, these are listed next to the respective colors. **Requirements for a Light to Be Seen at a Given Distance**: 1. The light must be above the observer's apparent horizon. 2. The light must have sufficient luminous intensity. 3. Visibility must not be obscured by weather conditions. **Types of Range**: 1. **Geographic Range**: a. Depends on the height of the light, the observer's eye level, and atmospheric refraction. b. A table on Page A-18 provides geographic ranges based on the elevation of the light and the observer. Adjustments may be needed for tide levels. 2. **Luminous Range**: c. Determined by the light's luminous intensity, air clarity, and light characteristics (e.g., flash duration). d. Luminous intensity in candelas may be shown in italics under the light's description in column 4. e. Meteorological stations report visibility (in kilometers) on a 0-9 scale (code VV). **Luminous Range Example**: f. Using the diagram on Page A-19: i. For a nominal range of 10 M (or intensity of 1300 candelas) and visibility of 7 M, the luminous range is between 7 M and 8 M. g. Note: This is approximate as atmospheric transparency may vary. 3. **Nominal Range**: h. Defined by IALA as the luminous range of a light in a standard atmosphere with 10 M meteorological visibility.